Elastomer resonator for orbiting-mass oscillator

ABSTRACT

An orbiting-mass oscillator is coupled to a low-impedance elastomer in which a resonant standing-wave pattern can be established. The elastomer serves as a transmission and energy storage medium for the energy and is coupled to a free-standing heavy mass.

energy such as is generated in acoustic resonators. In the prior art, anacoustic generator, such as for example an orbitingmass oscillator, hasbeen coupled to an elastic material such as steel, in which astanding-wave pattern could be generated. Such systems are taught inmany of my issued patents wherein such combination of an orbiting-massoscillator together with an elastic material such as steel have beenutilized as an effective means for the transmission of resonant sonicenergy. Never before have the unusual advantages to be attained by usingan elastomeric material such as rubber for the resonator beenappreciated.

The herein invention utilizes elastomeric material as a resonatorelement in a system utilizing acoustic energy. Preferably, the resonatorelement comprises a hollow thickwalled cylinder of an elastomericmaterial such as rubber or a rubberlike synthetic or natural material.Affixed to one end of the cylinder is an oscillator for generatingacoustic waves in the resonator. Preferably, the oscillator is anorbiting-mass type such that a standing resonant wave is established andmaintained in the resonator column. In one embodiment of the invention,the resonator can be coupled to a heavy mass, which in turn can drive anelement such as a drill. The heavy mass between the elastomericresonator and the drill tool acts, as will be explained, as a rectifier.

It has also been found that the elastomeric material interposed betweenthe working tool and the support structure and housing therefor providesa compliant or low-impedance reactance which acts in the nature of acapacitive reflector to reflect the shock waves developed in the toolback to the tool so as to ameliorate their effects on the supportstructure and housing. lt is to be noted that a similar shock waveamelioration is attained in the device shown in FIG. 3 of my U.S. Pat.No. 3,342,076 by virtue of the capacitive reactance of relatively lowimpedance fluid in chamber 44 and the high inductive reactance of body55, and the device shown in FIG. 16 of my U.S. Pat. No. 3,352,369 byvirtue of the capacitive reactance of air in chamber 88 and the highinductive reactance of housing 82.

It is also to be noted that all of the following of my applicationsdisclose the above-indicated use of low-impedance material to provide acompliant reactance in combination with a massive housing: applicationSer. No. 19,078, filed Mar. 31, 1960, for Oscillatory Fluid StreamDriven Sonic Generator with Elastic Autoresonator, now U.S. Pat. No.3,111,931; application, Ser. No. 57,520, filed Sept. 21, 1960, for SonicEarth Boring Drill with Elastic Fluid Resonator, now U.S. Pat. No.3,163,240; application Ser. No. 443,997 for Sonic Driver with PneumaticCapacitance, filed Mar. 30, 1965, now U.S. Pat. No. 3,277,970;application Ser. No. 459,754, filed May 28, 1956, for Low Impedancelsolator for Vibratory Pile Driver Machines, now U.S. Pat. No.3,344,874; application Ser. No. 496,468, filed Oct. 15, 1965, for SonicResonator for Use with Sonically Driven Apparatus, now U.S. Pat. No.3,342,076; my application Ser. No. 441,209, filed Mar. 19, 1965 forSonic Method and Apparatus for Driving Anchors, Anchor Posts and theLike, now U.S. Pat. No. 3,352,369; my application Ser. No. 34,805 filedJuly 12, 1954, for Sonic Drilling by Rotating the Tool, now U.S. Pat.No. 3,211,243; my application Ser. No. 759,110, filed Sept. 11, 1968,for Method for Providing Efficient Sonic Coupling to the Earth in aSeismic Survey System, now U.S. Pat. No. 3,504,756; and my copendingapplication Ser. No. 816,890, filed Apr. 17 1969.

It is believed the invention will be better understood from thefollowing detailed description and drawing of which:

The sole FIG. is a partially sectional view of an embodiment of thisinvention showing the elastomeric resonator utilized in combination witha drill.

It is helpful to the comprehension of this invention to make an analogybetween a mechanical resonant circuit and an electrical resonantcircuit. This type of analogy is well known to those skilled in the artand is described, for example, in Chapter 2 of Sonics" by Hueter andBolt, published in 1955 by John Wiley and Sons. In making such ananalogy, force F is equated with electrical voltage E, velocity ofvibration u is equated with electrical current i, mechanical complianceC,, is equated with electrical capacitance C,, mass M is equated withelectrical inductance L, mechanical resistance (friction)- R,,, isequated with electrical resistance R, and mechanical impedance Z, isequated with electrical impedance Z,,. Thus, it can be shown that, if amember is elastically vibrated by a sinusoidal force, F,,sinwt, in beingequal to 2 rr times the frequency of vibration, then Where wM is equalto l/wC,,,, a resonant condition exists, and the effective mechanicalimpedance Z, is equal to the mechanical resistance R,,,, the reactiveimpedance components wM and 1 lwC cancelling each other out. Under sucha resonant condition, velocity of vibration u is at a maximum, effectivepower factor is unity, and energy is most efficiently delivered to theobject being vibrated. It is such a high-efficiency resonant conditionin the elastic system being driven that is preferably utilized in themethods and devices of this invention to achieve the desired endresults.

It is to be noted by reference to equation 1 that velocity of vibrationu is highest where impedance Z is lowest, and vice versa. Therefore, ahigh-impedance load will tend to vibrate at relatively low velocity, andvice versa. Thus, at an interface between highand low-impedanceelements, a high relative movement results by virtue of such impedancemismatch which, as in the equivalent electrical circuit, results in ahigh reflected wave. This is accomplished in the embodiment of theinvention where the elastomer resonator is coupled to a heavy mass whichin turn is affixed to a chisel drill. High relative movement between theelastomer-coupled mass and drill results. Alternatively, where alow-impedance load, such as water, is present, the acoustic impedance ofthe elastomer so closely matches that maximum transfer of the vibratoryener gy is achieved. The mismatch of impedance arises at the interfaceof the water and parts submerged therein wherein the desired cleaningcan occur.

Just as the sharpness of resonance of an electrical circuit is definedas the Q thereof, and is indicative of the ratio of energy stored to theenergy used in each cycle, so also the Q of a mechanical resonantcircuit has the same significance and is equal to the ratio between mMand R,,,. Thus, high efficiency and considerable cyclic motion can beachieved by designing the mechanical resonant circuit for high Q.

Of particular significance in the implementation of the methods anddevices of this invention is the high acceleration of the components ofthe elastic resonant system that can be achieved at sonic frequencies.It can be shown that the acceleration of a vibrating mass is a functionof the square of the square of the frequency of the drive signal timesthe amplitude of vibration. Under resonant conditions, the amplitude ofvibration is at maximum and thus even at moderately high sonicfrequencies very high accelerations are achieved.

In considering equation 1, several factors are to be noted. First, thisequation represents the total effective resistance, mass and compliancein a vibrating circuit, and these parameters are generally distributedthroughout the system rather than being lumped in any one component orportion thereof. Secondly, the vibrating system often includessurrounding components, a container holding the water and the wateritself.

It is also to be noted that orbiting-mass oscillators are utilized inthe devices of the invention that automatically adjust their outputfrequencies to maintain resonance with changes in the characteristics ofthe load. Thus, in situations where we are dealing with parts which areplaced in a bath during the operation of the device which will changethat load, the system automatically is maintained in optimum resonantoperation by virtue of the lock in characteristics of applicantsorbiting-mass oscillators. The vibrational outputs from suchorbiting-mass oscillators are generated along a controlled predeterminedcoherent path to provide maximum output along a desired axis or axes.The orbitingmass oscillator automatically changes not only its frequencybut its phase angle and therefore its power factor with changes in theresistive impedance load to assure optimum efficiency of operation atall times. Such orbiting-mass oscillators are capable of efficientlygenerating high-level vibrational outputs.

By utilizing as a resonator element an elastomeric material such asrubber, a much greater feedback to the oscillator is accomplished thanwhen the resonator is of a high-impedance material such as, for example,a steel column. This feedback results, since the elastomer, because ofits inherently low impedance, provides a greater cyclic stroke for agiven frequency at the point where the oscillator is connected.Previously,

other low-impedance resonator elements such as air springs have beenaffixed to an oscillator. However, these elements have lumped constantimpedance characteristics. On the other hand, the elastomeric materialis a distributed constant system. A distributed constant system has theadvantage of being able to accomplish an acoustic lever effect where,for example, a high velocity or amplitude vibration at the interface ofthe oscillator can be converted to a low velocity with a high force atthe end of the resonator exposed to the load element.

Further, as indicated, one of the advantages of an orbitingmassoscillator is its lock-in characteristics with the automatic adjustmentof operating frequencies to accommodate for sudden changes inenvironmental reactive impedance. This feedback is best accomplished bya low-impedance resonator, such as the elastomeric element disclosedwhich has a large-amplitude vibration to better accomplish the feedback.Additionally, in this same vein, the automatic accommodation for changesin environmental resistive impedance caused by a work load is better fedback to the oscillator through a low-impedance resonator since there isgreater activity where the resonator is coupled.

Turning now to the FlG., a C-shaped handle 91 is connected at a firstend 93 to a plate 95 for supporting a motor 97. Extending downwardlyfrom plate 95 and integrally formed therewith is an arm 99 connected ata pivot point 101 to a movable arm 103 which in turn is affixed to adrill chisel 105. Attached to a second end 107 of the handle 91 is asupport arm 109 extending downwardly to an attachment ring 111 which maybe of metal. The ring 111 surrounds and helps to support a tubularshaped elastomeric resonator 113. A portion of the ring 111 isadditionally affixed to the arm 99 and connected therewith by means ofbolts 1 14. Motor 97 drives oscillator 115 through a flexible shaft 117connected therebetween. The output of oscillator 15 is coupled to aplaten 119 affixed to the top of the resonator element 13. The bottom ofthe resonator element is connected to a second platen 121 having a heavymass 123 affixed thereto. Platens 119 and 121 are preferably vulcanizedor glued with an epoxy resin to the elastomeric resonator 113 an thusintegrally connected therewith. Heavy mass 123 is in contact with araised portion 125 of the movable arm 103 directly in line with thechisel drill 105.

In the operation of the device, the motor which can be driven by meansof electrical power provided through line 127 drives orbiting-massoscillator 115, which may be of the type described in my U.S. Pat. No.3,217,551, causing a standing wave 129 to be developed in the resonatorelement 113. The resonator element in turn drives heavy mass 123 againstthe raised portion 125 above the chisel drill. Since the mzsis notattached to the portion 125 and the general movement of the resonator isin a vertical direction, the chisel drill will only move downwardly rnresponse to the downward vibratory excursions of mass 123, causing asolely unidirectional action of the chisel drill. In this manner,effective rectification of the sonic energy is achieved. Pivot 101permits the arm 103 to move the chisel drill downward into the ground asthe heavy mass 123 strikes the portion 125 during the downward vibratoryexcursions of the resonator. Ring 111 surrounds the resonator element113 at a nodal point so that a minimum or virtually no vibrationalenergy is dissipated into support arms 99 and 109 or carried back toparts such as handle 91.

It is to be noted that, while the device of the invention has beendescribed as utilized in a chisel drill, the vibrational drive systemdisclosed can be utilized to equal advantage for driving other types ofdevices such as riveters, scrapers, woodworking tools, and the like.

I claim:

1. ln combination,

an orbiting-mass oscillator,

an element to be energized,

an elastomeric resonator element coupled in series between said elementto be energized and said oscillator as a positive linkage therebetween,and

mans for driving said oscillator at a frequency such as to causeresonant elastic vibration of said resonator element,

whereby substantially all of the vibratory energy generated by saidoscillator is transmitted therefrom through said resonator element tosaid element to be energized. 2. The combination of claim 1 wherein saidelement is tubular.

3. The combination of claim 1 wherein said resonator element is coupledat one end to said oscillator, said element to be energized comprising aheavy mass coupled to the other end of said resonator element.

4. The combination of claim 3 and further comprising a tool disposedadjacent to said heavy mass, said tool contacting said mass whereby whensaid mass is caused to vibrate said tool will move in only onedirection.

1. In combination, an orbiting-mass oscillator, an element to beenergized, an elastomeric resonator element coupled in series betweensaid element to be energized and said oscillator as a positive linkagetherebetween, and mans for driving said oscillator at a frequency suchas to cause resonant elastic vibration of said resonator element,whereby substantially all of the vibratory energy generated by saidoscillator is transmitted therefrom through said resonator element tosaid element to be energized.
 2. The combination of claim 1 wherein saidelement is tubular.
 3. The combination of claim 1 wherein said resonatorelement is coupled at one end to said oscillator, said element to beenergized comprising a heavy mass coupled to the other end of saidresonator element.
 4. The combinaTion of claim 3 and further comprisinga tool disposed adjacent to said heavy mass, said tool contacting saidmass whereby when said mass is caused to vibrate said tool will move inonly one direction.